KR20060042397A - Switching regulator and image forming apparatus and its control method - Google Patents

Abstract

The switching regulator inputs a voltage applied to the rectifying diode 7 connected in series with the secondary side of the transformer and generates a voltage signal Vvp corresponding to the voltage, and a voltage generated by the input voltage detecting circuit. And a calculation unit 100 for calculating a voltage value Vin input to the primary side of the transformer based on the voltage value of the voltage signal.

Image Forming Devices, Switching Regulators, Transformers, Rectifier Diodes, Current Transformers, Photocouplers

Description

Switching regulator and image forming apparatus and control method thereof {SWITCHING REGULATOR AND IMAGE FORMING APPARATUS AND ITS CONTROL METHOD}

1 is a block diagram showing the configuration of a switching regulator and an input voltage detection circuit according to a first embodiment of the present invention.

2 is a waveform diagram showing an anode voltage of a secondary rectifying diode according to a first embodiment.

3A to 3C are signal waveform diagrams showing the operation of the switching regulator and the input voltage detection circuit according to the first embodiment.

4 is a block diagram showing the configuration of a switching regulator, an input voltage detection circuit and an input current detection circuit according to a second embodiment of the present invention.

5 is a waveform diagram illustrating an anode voltage of a secondary rectifying diode according to a second exemplary embodiment of the present invention.

6A to 6C are signal waveform diagrams showing the operation of the switching regulator and the input current detection circuit according to the second embodiment.

7 is a block diagram showing the configuration of a switching regulator and an output current detection circuit according to a third embodiment of the present invention.

8 is a waveform diagram illustrating an anode voltage of a secondary rectifying diode according to a third exemplary embodiment of the present invention.

Fig. 9 is a block diagram for explaining a configuration around a power supply in the image forming apparatus according to the fourth embodiment of the present invention.

10A and 10B are waveform diagrams showing the operation of the image forming apparatus according to the fourth embodiment.

Fig. 11 is a block diagram showing a configuration around a power supply of a conventional image forming apparatus.

Fig. 12 is a block diagram showing a configuration around a power supply of a conventional image forming apparatus.

Fig. 13 is a block diagram showing a configuration around a power supply of a conventional image forming apparatus.

14A and 14B are waveform diagrams showing power supply control by a fixing unit in a conventional image forming apparatus.

Fig. 15 is a flowchart showing power supply control by the fixing unit in the image forming apparatus according to the fourth embodiment.

 <Explanation of symbols for main parts of drawing>

1: commercial power

2: rectification bridge

3: Primary smoothing capacitor

4: driving circuit

5: transformer

6: FET

7: rectifier diode

8: 2nd smoothing capacitor

9: load

The present invention relates to a switching regulator for rectifying, smoothing and switching a commercial power supply voltage and inputting the voltage to the primary side of the transformer to generate a predetermined direct current voltage at the secondary side of the transformer, and a control method of the switching regulator. The present invention also relates to an image forming apparatus equipped with such a switching regulator and a control method of the apparatus.

For the protection of the elements in the switching regulator circuit or the operation control of the load on the secondary side, the voltage value of the commercial power supply, the current value input to the switching regulator, and the current value output from the switching regulator are detected. As a method of detecting a voltage value or a current value of a commercial power supply input to a switching regulator, a method of using a photocoupler and a current transformer has been proposed (see Document 1).

Document 1 JP 10-274901 A

The conventional method will be described with reference to FIG.

The AC voltage supplied from the commercial power supply 1 is rectified and smoothed by the rectification bridge 2 and the primary smoothing capacitor 3, and becomes almost constant voltage Vp. The voltage Vp is supplied to the FET 6 through the transformer 5. By switching the FET 6 by the drive circuit 4, a pulse voltage is caused on the secondary side of the transformer 5. The pulse voltage thus caused is rectified and smoothed by the secondary rectifying diode 7 and the secondary smoothing capacitor 8, resulting in a predetermined voltage Vout. This voltage Vout is supplied to the load 9.

Next, the method of detecting the voltage value of the commercial power supply 1 in this switching regulator is demonstrated.

The primary voltage Vp is divided by the resistor 17 and the resistor 18 and supplied to the LED of the photocoupler 13. Since the amount of light emitted from the LED of the photocoupler 13 is proportional to the voltage Vp, the collector current of the phototransistor of the photocoupler 13 is also proportional to this voltage Vp. Therefore, the voltage value Vvp supplied to the calculation unit 10 is proportional to the primary voltage value Vp. The calculation unit 10 calculates the voltage value of the commercial power supply 1 by inverting the primary voltage value Vp from the resistance values of the resistors 17 and 180 and the photocurrent conversion efficiency (CTR value) of the photocoupler 13. You can get Vin.

Next, a method of detecting the current value input to the switching regulator will be described.

The primary terminal of the current transformer 11 is connected to the input of the switching regulator. Therefore, a current proportional to the input AC current value Iin flows through the secondary terminal of the current transformer 11. This current is converted into a voltage by the resistor 12 and supplied to the differential amplifier 14. The output voltage Viin from the differential amplifier 14 is smoothed by the resistor 16 and the capacitor 190 and supplied to the calculation unit 10. Based on this voltage Viin, the calculation unit 10 calculates a current value Iin input to the switching regulator by inverting from the winding ratio of the current transformer 11 and the resistance value of the resistor 12.

Moreover, as a method of detecting the current value output from a switching regulator, the method of using a current detection resistor was proposed (refer document 2).

[Document 2] JP 05-076173 A

Next, with reference to FIG. 12, the method of detecting the current value output from a switching regulator is demonstrated.

The current detection resistor 340 is connected to the output of the switching regulator. A voltage Viout proportional to the output current Iout from the switching regulator is generated at both ends of the current detection resistor 340. This voltage Viout is detected by the differential amplifier 33 and supplied to the arithmetic unit 10. The calculation unit 10 converts this voltage Viout into a digital signal and calculates the output current value Iout output from the switching regulator by inverting (Viout / R) the resistance value R of the current detection resistor 340.

In addition, in FIG. 11, the control in the case where a switching regulator is mounted in an image forming apparatus (for example, a laser beam printer) is demonstrated with reference to FIG.

In FIG. 13, the commercial power supply 1 is supplied to the switching regulator and the settling power supply 34 shown in FIG. 11, and the actuator 36 is connected to the secondary side of the transformer 5 instead of the load 8 in FIG. 11. .

Commercial power supply 1 is supplied to the switching regulator and also to the settling power supply 34. The output from the fixing power supply 34 is supplied to the fixing unit 37. The fixing unit 37 fuses the toner image and fixes the image on the paper surface. The calculation unit 10 is fixed from the fixing power supply 34 so that the fixing unit 37 is at a substantially constant temperature based on the temperature information signal thm supplied from a temperature detection unit (not shown) installed in the fixing unit 37. The output power to the unit 37 is turned on / off. At this time, the on / off timing of the fixing power supply 34 is defined by the on / off signal ON / OFF supplied from the calculating unit 10 to the fixing power supply 34. The output power from the fixing power supply 34 is defined by the power upper limit signal Pwtgt.

In general, the maximum current value Imax is defined by the safety standard for the current value that can be consumed by the electric appliance from the commercial power supply 1. For example, the current value consumed by electrical equipment from commercial outlets in Japan is up to 15A. Therefore, the calculation unit 10 sequentially calculates the power upper limit signal Pwtgt and supplies it to the fixing unit 37 so that the current input from the commercial power supply 1 to the recall forming apparatus does not exceed the prescribed current value Imax. To control the power being generated. This operation will be described with reference to Figs. 14A and 14B.

Fig. 14A shows the transition of the current Iin input to the switching regulator. At timing T1, when the main switch (not shown) of the image forming apparatus is turned on, the calculating unit 10 operates the actuator 36 appropriately to prepare for the image forming operation. With this operation, the current Iin input to the switching regulator increases sequentially. The calculating unit 100 sequentially detects the input current value Iin and calculates a difference from the prescribed current value Imax, Itgt = Imax-Iin. That is, the difference Itgt is the allowable current value for the fixing unit 37. Further, the calculation unit 10 detects the input voltage Vin and calculates an allowable power Pwtgt = Itgt x Vin from the current value Itgt and the input voltage Vin.

 As shown in FIG. 14B, the calculation unit 10 controls ON / OFF the power Pwtgt input to the fixing unit 37 so that the temperature of the fixing unit 37 is approximately constant. By this configuration, the current input from the commercial power supply 1 to the image forming apparatus is controlled so as not to exceed the prescribed current value Imax.

However, the prior art had the following problems. First, when detecting the voltage value or the current value of the commercial power supply 1 input to the switching regulator, a primary secondary insulation component such as the photocoupler 13 and the current transformer 11 is required to increase the cost. Second, when detecting the current value output from the switching regulator, since the current detection resistor 340 is inserted into the output power line, power loss occurs in the current detection resistor 340. Third, due to the voltage drop generated in the current detection resistor 340, the accuracy of the output voltage from the switching regulator is reduced.

Finally, when such a conventional switching regulator is mounted on an image forming apparatus, a primary secondary insulation component such as a photocoupler 13 and a current transformer 11 is required, thereby increasing the cost. In order to maintain the specified current value of the commercial power supply without such a photocoupler and a current transformer, the maximum current value Iamax consumed by the actuator 36 is stored in the calculation unit 10, and the maximum value (Imax−) in the fixing unit 37 is stored. An image forming apparatus is also proposed in which power of Iamax) x Vinmin (Vinmin is the minimum value of the commercial power supply voltage) is supplied. However, in this configuration, when the current consumed by the actuator 36 is equal to or less than Iamax or when the commercial power supply voltage is higher than Vinmin, the current that can be sufficiently supplied from the commercial power supply 1 cannot be used efficiently. Due to this structure, the time (warm up time) until the temperature of the fixing unit 37 is increased to the temperature for the image forming operation after the main switch is turned on is increased.

The present invention has been made in view of the above problems, and one of its features is to solve the above-mentioned disadvantages of the prior art.

Another aspect of the present invention is to provide a switching regulator and an image forming apparatus for detecting a current output from the switching regulator while suppressing a power loss and a decrease in output voltage accuracy, and a control method thereof.

 According to the present invention, voltage waveform detecting means for inputting a voltage applied to a rectifying diode connected in series to a secondary side of a transformer and generating a voltage signal corresponding to the voltage; And control means for calculating a voltage value input to the primary side of the transformer based on the voltage value of the voltage signal generated by the voltage waveform detecting means.

Also, according to the present invention, there is provided a fixing apparatus, comprising: a fixing unit configured to fix a toner image formed on a recording medium by heat; A fixing power source configured to supply power to the fixing unit; An actuator configured to execute an image forming operation; A switching regulator configured to supply power to the actuator; Calculating means for obtaining a current value input to the switching regulator; And power control means for controlling the power supply by the fixing power source in accordance with the current value obtained by the computing means. An image forming apparatus for forming an image based on an electrophotographic system is provided.

The above features are attained by the combination of features recited in the independent claims and the dependent claims define only specific examples of the invention.

The above configuration is not exhaustive of the invention, and other combinations of the above features can be regarded as the invention.

Other features, objects, and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.

The accompanying drawings become part of the detailed description of the invention, together with the description of the invention illustrate embodiments of the invention and illustrate the principles of the invention.

<Example>

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples do not limit the invention described in the claims, and furthermore, not all combinations of the features described in the embodiments are essential to the solution according to the invention.

[First Embodiment]

1 is a block diagram showing the configuration of a switching regulator and an input voltage detection circuit according to a first embodiment of the present invention. In this embodiment, the switching regulator is applied to a fly-back type power supply having a fixed oscillation frequency. A characteristic characteristic of this embodiment is to monitor the anode voltage waveform of the secondary rectifying diode 7 to detect the voltage value of the commercial power supply from the negative peak value of the voltage waveform.

The AC voltage supplied from the commercial power supply 1 is rectified and smoothed by the rectification bridge 2 and the primary smoothing capacitor 3, and becomes a substantially constant voltage Vp. The voltage Vp is supplied to the FET 6 through the transformer 5. When switching occurs in the FET 6 by driving the drive circuit 4, a pulse voltage is induced on the secondary side of the transformer 5. The pulse voltage thus induced is rectified and smoothed by the secondary rectifying diode 7 and the secondary smoothing capacitor 8 to become a predetermined voltage Vout. The voltage Vout is supplied to the load 9.

An input voltage detection circuit 27 is connected to the anode terminal of the secondary rectifier diode 7. Hereinafter, the operation of the input voltage detection circuit 27 will be described with reference to FIGS. 2 and 3.

The input voltage detection circuit 27 includes a diode 19, an inverting amplifier circuit (resistors 20 and 21, an op amp 22), a peak hold circuit (diode 23, a capacitor 24, a resistor). (25)).

FIG. 2 is a waveform diagram illustrating the voltage change of the anode terminal of the secondary rectifying diode 7.

In Fig. 2, reference numeral 200 denotes the waveform of the anode voltage when the FET 6 is off, and reference numeral 201 denotes the waveform of the anode voltage when the FET 6 is on.

3 (a) to 3 (c) show changes in the voltage of the anode terminal of the secondary rectifying diode 7 and changes in the output voltage of the input voltage detection circuit 27 according to the on / off state of the FET 6. A signal waveform diagram is shown.

3A shows the gate voltage of the FET 6 driven by the drive circuit 4. When the gate voltage is high level, the FET 6 is turned on.

FIG. 3B shows the voltage waveform of the anode of the secondary rectifying diode 7 which changes in accordance with the gate voltage of the FET 6 in FIG. A waveform having an amplitude from (-V1ow) to (Vout + Vf) is obtained. The voltage Vf is the forward voltage of the secondary rectifying diode 7. The waveform of the anode voltage is sliced into only the negative (-) voltage portion by the diode 19 and input to the inverting amplifier circuit including the OP amplifier 22.

Fig. 3C shows the output of the inverted amplifier circuit as a pulse waveform shown by broken lines. At this time, the high level voltage Vvp of the pulse wave can be expressed by the following equation (1), assuming that the gain of the inverted amplifier circuit is?.

The voltage Vlow can be expressed as follows using the terminal voltage Vp of the primary electrolytic capacitor 3, the primary winding number N1 of the transformer 5, and the secondary winding number N2 of the transformer 5.

Further, the following equation (3) is established between the effective value Vin of the voltage of the commercial power supply 1 (sine wave voltage) and the terminal voltage Vp of the primary electrolytic capacitor 3.

Therefore, the following equations (4) and (5) are established.

That is, the effective value Vin of the voltage of the commercial power supply 1 becomes proportional to the high level voltage Vvp of the inverting amplifier circuit. The output pulse of this inverting amplifier circuit is converted into a DC voltage of approximately Vvp by the peak hold circuit, which will be described later, and input to the A / D conversion port of the calculation unit 10. The calculation unit 10 uses the gain α of the inverted amplification circuit, the primary winding number N1 of the transformer 5, the secondary winding number N2 of the transformer 5, and the output voltage value Vvp to obtain the voltage of the commercial power supply. Vin can be obtained (α, N1, N2 are defined above).

The configuration of the switching regulator, the input voltage detection circuit, and the like described in the first embodiment can be changed as appropriate, and the present invention is not limited.

As described above, according to the first embodiment, the primary-secondary insulation parts such as photocouplers and current transformers required in the prior art can be omitted. In addition, even when detecting the current value and the voltage value output from the switching regulator, it is not necessary to insert a current detection resistor that causes power loss in the output power supply line, thereby reducing the input voltage value and the input current value without losing power. Can be obtained with high precision.

Second Embodiment

4 is a block diagram illustrating a switching regulator according to a second embodiment of the present invention. In Fig. 4, the components corresponding to Fig. 1 have the same reference numerals and their description is omitted. In the second embodiment, the switching regulator is applied to a flyback type power supply having a fixed oscillation frequency. As in the case of the first embodiment, the input voltage value from the commercial power supply 1 is detected, the anode voltage waveform of the secondary rectifying diode 7 is monitored, and the current value input to the switching regulator from the negative pulse width is determined. Detect.

Hereinafter, the operation of the input current detection circuit 35 will be described with reference to FIGS. 4 and 5 and 6 (a) to (c). In FIG. 4, operations other than the operation of the input current detection circuit 35 are similar to those of the first embodiment, and thus description thereof is omitted.

The input current detection circuit 35 includes a diode 18 and an integrating circuit (zenner diode 30, resistors 26, 28, 31, capacitor 32, and OP amplifier 29).

5 is a waveform diagram showing the anode voltage of the secondary rectifying diode 7 according to the second embodiment of the present invention. As in the case of FIG. 2 described above, in the waveform 501 of the anode voltage when the FET 6 is on, its pulse width is proportional to 1/2 the input current.

FIG. 6A shows the gate voltage of the FET 6 driven by the drive circuit 4. When the gate voltage is high level, the FET 6 is turned on.

FIG. 6B shows the voltage waveform of the anode of the secondary rectifying diode 7 having an amplitude from (−V1ow) to (Vout + Vf). This voltage is sliced into the negative voltage portion only by the diode 18 and clamped to the voltage (-Vz) by the zener diode 30. Therefore, as shown in Fig. 6C, the input voltage of the integrating circuit including the OP amplifier 29 has a pulse waveform from amplitude 0 [V] to (-Vz).

In this waveform, assuming that the negative pulse width is t1, the period is t2, and the gain of the integrating circuit is β, the output voltage Viin from the integrating circuit is expressed as follows.

Therefore, the negative pulse width t1 is expressed as follows.

The input current Iin of the flyback power supply is expressed using the pulse width t1, the commercial power supply voltage Vin, and the primary inductance L1 of the transformer 5.

Therefore, the input current Iin is expressed as follows.

That is, the input current Iin from the commercial power supply 1 is proportional to the square Viin ² of the output voltage Viin of the integrating circuit.

The output Viin is input to the A / D conversion port of the calculation unit 10. The calculating unit 10 is obtained from the A / D converted output voltage Viin of the integrating circuit, the commercial power supply voltage Vin described above, and other constants (t2, L1, β, Vz are already defined), The input current Iin can be obtained by

The configurations of the present switching regulator, the input voltage detection circuit and the input current detection circuit can be appropriately changed and do not limit the scope of the present invention.

As described above, according to the second embodiment, the primary-secondary insulating parts such as photocouplers and current transformers required in the prior art may be omitted. In addition, even when detecting the current value and the voltage value output from the switching regulator, since there is no need to insert a current detection resistor that causes power loss in the output power line, the input voltage value and the input current value with high accuracy without power loss. Can be obtained.

Third Embodiment

7 is a block diagram showing the configuration of a switching regulator according to a third embodiment of the present invention. In Fig. 7, the components corresponding to Fig. 1 have the same reference numerals, and their description is omitted. In a third embodiment, the switching regulator is applied to a flyback power supply with a fixed oscillation frequency. The characteristic characteristic of this embodiment is to monitor the waveform of the anode voltage of the secondary rectifying diode 7 so that the current value Iout output from the switching regulator is detected from the positive voltage width of the anode.

Hereinafter, the operation of the output current detection circuit 40 will be described with reference to FIG. 8. Components other than this output current detection circuit 40 are the same as that of 1st Embodiment mentioned above, and their description is abbreviate | omitted.

The output current detection circuit 40 includes a timer unit 320. The timer unit 320 monitors the waveform of the anode voltage of the secondary rectifying diode 7, and outputs the time t3 of the positive pulse width to the calculation unit 10. The time measurement operation by the timer unit 320 may be executed by the calculation unit 10.

8 is a waveform diagram showing the anode voltage of the secondary rectifying diode 7 corresponding to the output from the flyback power supply. In Fig. 8, reference numeral 801 denotes a state in which the anode voltage is positive, and reference numeral 802 denotes a state in which the anode voltage is negative.

The output current Iout is expressed as follows using the time t3 at which the anode voltage is positive, the switching period t2, the secondary inductance L2 of the transformer 5, the output voltage Vout, and the forward voltage Vf of the secondary rectifying diode.

That is, the output current Iout is proportional to the square (t ₃ ² ) of the time t ₃ at which the anode voltage is positive. Therefore, the calculation unit 10 calculates the output current Iout from the time t3 and other constants t2, L2, Vout, and Vf by equation (10).

The configuration of the present switching regulator, the output current detection circuit can be changed as appropriate, and does not limit the present invention.

As described above, according to the third embodiment, the primary-secondary insulating parts such as photocouplers and current transformers required in the prior art may be omitted. In addition, even when detecting a current value or a voltage value output from the switching regulator, it is not necessary to insert a current detection resistor that causes power loss in the output power supply line, so that the input voltage value and the input current value with high accuracy without power loss are required. Can be obtained.

[Example 4]

9 is a block diagram illustrating an image forming apparatus according to a fourth embodiment of the present invention. In the fourth embodiment, the switching regulator described in the second embodiment (Fig. 4) is used as the power source for the actuator of the image forming apparatus. A method of controlling the fixing unit of the image forming apparatus based on the commercial power supply voltage value and the input current value detected by the switching regulator will be described. Since the method of detecting the input current value Iin and the commercial power supply voltage value Vin by the switching regulator is the same as that described in the first and second embodiments, the description is omitted.

The output voltage Vout from the switching regulator is supplied to the actuator 36. This actuator 36 executes an image forming operation based on the control of the computing unit 10. The commercial power supply 1 is supplied to the switching regulator and also to the fixing power supply 34. The output from the fixing power supply 34 is supplied to the fixing unit 37. The fixing unit 37 fuses and fixes the toner image on the sheet of paper. The arithmetic unit 10 is based on the temperature information signal thm 901 supplied from a temperature detection unit (not shown) installed in the fixing unit 37, so that the fixing unit 37 has a substantially constant temperature. ), The output power to the fixing unit 37 is turned on / off. At this time, the timing of the on / off of the fixing power supply 34 is defined by the on / off signal 902 supplied from the calculating unit 10 to the fixing power supply 34. The output power of the fixing power supply 34 is defined by the power upper limit signal Pwtgt 903.

In general, the current value that can be consumed by the electric appliance from the commercial power supply 1 is defined by the safety standard as the maximum current value Imax. For example, the current value consumed by electrical equipment from commercial outlets in Japan is up to 15A.

Therefore, the calculation unit 10 sequentially calculates the power upper limit signal Pwtgt so that the current input from the commercial power supply 1 to the image forming apparatus does not exceed the prescribed current value Imax, and is supplied to the fixing unit 37. Control power.

This operation will be described with reference to FIGS. 10A and 10B.

10A illustrates a transition of the current Iin input to the switching regulator. When the main switch (not shown) of the image forming apparatus is turned on at the timing T1, the calculation unit 10 operates the actuator 36 appropriately to prepare for the image forming operation. According to this operation, the current Iin input to the switching regulator changes sequentially. The calculating unit 10 detects this current value Iin sequentially (second embodiment), and calculates the difference Itgt (= Imax-Iin) with the prescribed current value Imax. That is, this current difference Itgt is a current value that can be supplied to the fixing unit 37. Further, the calculation unit 10 detects the input voltage Vin (first embodiment), and calculates the power Pwtgt (= Itgt × Vin) which can be supplied to the fixing unit 37 from this current value Itgt and the input voltage Vin.

As shown in FIG. 10B, the calculation unit 10 controls ON / OFF the power Pwtgt 903 input to the fixing power supply 34 so that the temperature of the fixing unit 37 is approximately constant. In this configuration, the current input from the commercial power supply 1 to the image forming apparatus is controlled so as not to exceed the prescribed value Imax.

According to the fourth embodiment, the current input to the actuator switching regulator and the commercial power supply voltage input to the image forming apparatus are sequentially detected without the primary secondary insulation components such as photocouplers and current transformers required in the prior art. . In addition, since no current that can be supplied from a commercial power supply is wasted, the time (warming up time) from the on state of the main switch until the temperature of the fixing unit 37 is increased to the temperature for the image forming operation can be reduced.

FIG. 15 is a flowchart showing a control process of the calculation unit 10 for controlling the fixing unit 37 in the image forming apparatus according to the fourth embodiment. The program which executes this process is stored in the program memory (not shown) of the calculation unit 10.

This process is started by, for example, turning on the power of the apparatus. First, in step S1, the voltage value Vvp output from the input voltage detection circuit 27 is input, and the input voltage Vin is calculated based on the above expression (5) (step S2). Next, in step S3, the voltage value Viin output from the input current detection circuit 35 is input, and the input current Iin is calculated based on the above formula (9) (step S4). Then, in step S5, the current difference Itgt (= Imax-Iin) with the prescribed current value Imax is calculated, and in step S6, the power Pwtgt (= Itgt x Vin) that can be supplied to the fixing unit 37 is calculated. The fixing power source 34 is controlled based on the supplyable power Pwtgt to control the power supplied to the fixing unit 37. Next, in step S7, it is determined whether or not the temperature of the fixing unit 37 is within a predetermined range. If the temperature is within a predetermined range (sufficiently heated), the process proceeds to step S8 to interrupt the power supply to the fixing unit 37 and proceeds to step S1.

On the other hand, when the temperature of the fixing unit 37 does not fall within a predetermined range, the process proceeds to step S1 and the above-described process is repeatedly executed.

The present invention is not limited to the living embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention, the following claims are made.

According to the present invention, in detecting a voltage value of a commercial power source inputted to a switching regulator or a current value inputted to a switching regulator, it is possible to reduce costs by eliminating the use of primary-secondary insulation components such as photocouplers and current transformers. Can be. In addition, in detecting the current value output from the switching regulator, the current detection resistor can be omitted, thereby reducing power loss, and since there is no voltage drop in the general detection resistor, the output voltage from the switching regulator can be detected with high accuracy. As a result, the voltage and current values input to the switching regulator can be obtained with high accuracy.

Claims (24)

In the switching regulator, Voltage waveform detection means for inputting a voltage applied to a rectifying diode connected in series to the secondary side of the transformer and generating a voltage signal corresponding to the voltage; And Control means for calculating a voltage value input to the primary side of the transformer based on the voltage value of the voltage signal generated by the voltage waveform detecting means Switching regulator comprising a. According to claim 1, wherein the voltage waveform detecting means, An amplifier circuit configured to input and amplify the voltage applied to the rectifier diode; And Holding circuit configured to hold an output from the amplifier circuit Switching regulator having a. The control means according to claim 2, wherein the voltage means of the voltage signal is Vvp and the voltage value input to the primary side of the transformer is Vin.

To calculate the voltage value Vin by - where, N1 is the primary number of turns of the transformer, N2 is the secondary-side winding number of the transformer, wherein α is the gain of the amplifier circuit being - switching regulator. The method of claim 1, A clamp circuit configured to clamp the voltage applied to the rectifier diode connected in series with the secondary side of the transformer; An integrating circuit configured to input and integrate a voltage signal clamped by the clamp circuit; And Second control means for calculating a current value input to the primary side of the transformer based on a period of the voltage value input to the primary side of the transformer and the voltage signal integrated by the integrating circuit. Switching regulator further comprising. The voltage value of the voltage signal according to claim 4, wherein the current value input to the primary side of the transformer is Iin, the voltage value input to the primary side of the transformer is Vin, and the voltage value of the voltage signal integrated by the integrating circuit. Is Viin, and assuming that the clamp voltage value by the clamp circuit is Vz, the second control means

By calculating the current value Iin - where, L1 is the primary inductance of the transformer, β is the gain of the integration circuit, t2 is a period of the voltage signal Im-switching regulator. In the switching regulator, Time measuring means for measuring a pulse width of a voltage applied to a rectifying diode connected in series with a secondary side of the transformer; And Control means for calculating a secondary output current value of the transformer based on the secondary output voltage of the transformer and the pulse width measured by the time measuring means Switching regulator comprising a. The secondary output current value of the transformer is Iout, the secondary inductance of the transformer is L2, the secondary output voltage of the transformer is Vout, the pulse width is t3, and the period is t2. Assume that the control means,

Calculating the output current value Iout, where Vf is the forward voltage of the rectifying diode. 2. The switching regulator as claimed in claim 1, wherein said voltage waveform detecting means detects a negative (-) peak voltage value of a voltage applied to an anode of said rectifying diode. 5. The switching regulator as claimed in claim 4, wherein said voltage waveform detecting means detects a negative pulse width of a voltage applied to an anode of said rectifying diode. 7. The switching regulator as claimed in claim 6, wherein said time measuring means detects a positive pulse width of a voltage applied to an anode of said rectifying diode. The switching regulator of claim 1, wherein the switching regulator performs a fly-back conversion. An image forming apparatus for forming an image based on an electrophotographic method, A fixing unit configured to fix the toner image formed on the recording medium by heat; A fixing power source configured to supply power to the fixing unit; An actuator configured to execute an image forming operation; A switching regulator configured to supply power to the actuator; Calculating means for obtaining a current value input to the switching regulator; And Power control means for controlling the power supply by the fixing power source in accordance with the current value obtained by the calculation means Image forming apparatus comprising a. In the control method of the switching regulator, A voltage waveform detecting step of inputting a voltage applied to a rectifying diode connected in series to the secondary side of the transformer and generating a voltage signal corresponding to the voltage; And A control step of calculating the voltage value input to the primary side of the transformer, based on the voltage value of the voltage signal generated in the voltage waveform detection step Switching regulator control method comprising a. The method of claim 13, wherein the detecting of the voltage waveform comprises: An amplifying step of amplifying the voltage applied to the rectifying diode; And A holding step of holding the voltage amplified in the amplifying step Switching regulator control method comprising a. The voltage value Vin of claim 14, wherein the voltage value of the voltage signal is Vvp and the voltage value input to the primary side of the transformer is Vin.

Where N1 is the primary number of turns of the transformer, N2 is the secondary number of turns of the transformer, and α is the gain of the amplifying step. The method of claim 13, Clamping a voltage applied to the rectifier diode connected in series with the secondary side of the transformer; An integrating step of integrating the clamped voltage signal; And A second control step of calculating a current value input to the primary side of the transformer based on the voltage value input to the primary side of the transformer and the period of the voltage signal integrated in the integration step Switching regulator control method further comprising. 17. The voltage value of the voltage signal of claim 16, wherein the current value input to the primary side of the transformer is Iin, the voltage value input to the primary side of the transformer is Vin, and the voltage value of the voltage signal integrated in the integration step is Viin, and assuming that the clamp voltage value in the clamping step is Vz, the current value Iin is determined in the second control step.

Where L1 is the primary inductance of the transformer, β is the gain of the integration step, t2 is the period of the voltage signal. In the control method of the switching regulator, A time measuring step of measuring a pulse width of a voltage applied to the rectifier diode connected in series with the secondary side of the transformer; And  A control step of calculating an output current value of the secondary side of the transformer based on the pulse width measured in the time measuring step and an output voltage of the secondary side of the transformer Switching regulator control method comprising a. 19. The method of claim 18, wherein the output current value at the secondary side of the transformer is Iout, the secondary inductance of the transformer is L2, the output voltage at the secondary side of the transformer is Vout, and the pulse width is t3. , Assuming that the period is t2, the output current value Iout in the control step,

Calculated by the Vf is the forward voltage of the rectifying diode. The switching regulator control method according to claim 13, wherein in the voltage waveform detecting step, a negative peak voltage value of a voltage applied to an anode of the rectifying diode is detected. The method of claim 16, wherein in the voltage waveform detecting step, a negative pulse width of a voltage applied to an anode of the rectifying diode is detected. 19. The method of claim 18, wherein in the time measurement step, a positive pulse width of a voltage applied to the anode of the rectifying diode is detected. 14. The method of claim 13 wherein the switching regulator performs a flyback power conversion. An image forming apparatus comprising a fixing unit for fixing a toner image formed on a recording medium by heat, a fixing power supply for supplying power to the fixing unit, an actuator for performing an image forming operation, and a switching regulator for supplying power to the actuator Control method of Calculating a current value input to the switching regulator; And A power control step of controlling the power supply by the fixing power source according to the current value obtained in the calculation step An image forming apparatus control method comprising a.

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